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Identification of the major in vivo ABl-42-degrading catabolic-system in brain parenchyma.

脑实质中主要的体内ABl-42降解分解代谢系统的鉴定。

基本信息

批准号：
12672167
负责人：
IWATA Nobuhisa
金额：
$ 2.5万
依托单位：
The Institute of Physical and Chemical Research
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Accumulation of amyloid-pβ peptide (Ap) in brain triggers the pathological cascade leading to Alzheimer' s disease. To examine the mechanism of AB catabolism, we analysed the fate of multiply radio-labeled 3H/14C-Aβl-42 injected into rat hippocampus and identified neutral endopeptidase (s) similar or identical to neprilysin as the rate-1imiting peptidase using a panel of peptidase inhibitors. Chronic infusion of thiorphan, a specific inhibitor of neprilysin, into rat hippocampus caused accumulation of endogenous AB. To further identify the thiorphan-sensitive peptidase, we analysed ABl-42 catabolism by six recombinant thiorphan-sensitive peptidases in neutral endopeptidase family. Neprilysin degraded AB most rapidly and efficiently among them. Neprilysin-deficient mice showed significantly reduced ability to catabolize AB. We also observed a gene dosage-dependent clevation of the endogenous AB levels (-/- > +/- > +/+) in the mouse brains. The increase in the AB42 level in the neprilysin-deficient mouse brain was comparable to that in the mice carrying PSI mutation. Moreover, the regional Ap levels in wild-type mouse brain were in the order of hippocampus > cortex > striatum/thalamus > cerebellum and this tendency was markedly exaggerated in the neprilysin-deficient mice. In the experiments using aged mice, neprilysin activity and its protein content in hippocampus were reduced by 200% at 30 months-old ages, compared to 2 months-old ages. The neprilysin activity in cortex was also slightly but significantly reduced with aging, whereas those in other regions were not changed. These observations suggest that the neprilysin is the major AB-degrading enzyme in brain despite the molecular redundancy of the neprilysin family and that reduction of neprilysin activity particularly in the regions vulnerable to AB pathology will contribute to Alzheimer' s disease development by promoting AB deposition.

淀粉样蛋白 -pβ 肽 (Ap) 在大脑中的积累会引发导致阿尔茨海默病的病理级联反应。为了检查AB分解代谢的机制，我们分析了注射到大鼠海马体中的多重放射性标记的3H/14C-Aβ1-42的命运，并使用一组肽酶抑制剂鉴定了与脑啡肽酶相似或相同的中性内肽酶作为1速率限制肽酶。将脑啡肽酶特异性抑制剂噻吩嗪长期输注至大鼠海马会导致内源性 AB 积聚。为了进一步鉴定噻吩敏感肽酶，我们分析了中性内肽酶家族中六种重组噻吩敏感肽酶的ABl-42分解代谢。其中脑啡肽酶降解AB的速度最快、效率最高。脑啡肽酶缺陷小鼠的 AB 分解代谢能力显着降低。我们还在小鼠大脑中观察到内源性 AB 水平 (-/- > +/- > +/+) 的基因剂量依赖性裂解。缺乏脑啡肽酶的小鼠大脑中 AB42 水平的增加与携带 PSI 突变的小鼠相当。此外，野生型小鼠大脑中区域Ap水平的顺序为海马>皮质>纹状体/丘脑>小脑，并且这种趋势在脑啡肽酶缺陷小鼠中明显加剧。在使用老年小鼠的实验中，与 2 个月大的小鼠相比，30 个月大的小鼠海马体中脑啡肽酶活性及其蛋白质含量降低了 200%。随着年龄的增长，皮质中的脑啡肽酶活性也略有下降，但显着降低，而其他区域的脑啡肽酶活性则没有变化。这些观察结果表明，尽管脑啡肽酶家族存在分子冗余，但脑啡肽酶是大脑中主要的 AB 降解酶，并且脑啡肽酶活性的降低，特别是在易受 AB 病理影响的区域，将通过促进 AB 沉积而导致阿尔茨海默氏病的发展。